Light-emitting device and manufacturing method thereof

ABSTRACT

The present disclosure provides a light-emitting device comprises a substrate with a topmost surface; a first semiconductor stack arranged on the substrate, and comprising a first light-emitting layer separated from the topmost surface by a first distance; a second semiconductor stack arranged on the substrate, and comprising a second light-emitting layer separated from the topmost surface by a second distance; and a third semiconductor stack arranged on the substrate, and comprising third light-emitting layer separated from the topmost surface by a third distance; wherein the first semiconductor stack, the second semiconductor stack, and the third semiconductor stack are configured to emit different color lights; and wherein the second distance is different form the first distance and the third distance.

CROSS REFERENCE TO RELATED APPLICATIONS

This application a continuation application of U.S. patent application,Ser. No. 15/944,459, filed on Apr. 3, 2018, which is a continuationapplication of U.S. patent application Ser. No. 15/609,795, filed on May31, 2017, which is a continuation application of U.S. patent applicationSer. No. 14/901,415, now U.S. Pat. No. 9,705,029, filed on Dec. 28,2015, which claims the right of priority based on PCT application Ser.No. PCT/CN2013/078051 filed on Jun. 26, 2013; the content of which isincorporated herein by reference in its entirety.

FIELD OF DISCLOSURE

The present disclosure relates to a light-emitting device andmanufacturing method thereof, in particular to a light-emitting devicehaving a plurality of blocks of semiconductor stack and manufacturingmethod thereof.

BACKGROUND OF THE DISCLOSURE

A light-emitting diode (LED) is suitable for various lighting anddisplay applications because it has good opto-electrical characteristicsof low power consumption, low heat generation, long life, shocktolerance, compact, and swift response. A multi-cell light-emittingdevice is a device composed of multiple light-emitting diodes, such asan array of light-emitting diodes. With the development of technology inapplications, a multi-cell light-emitting device has a wider applicationin the market, for example, an optical display device, a traffic light,and a lighting apparatus. A lighting device of a High Voltage LED (HVLED) is one of the examples.

As shown in FIGS. 7A and 7B, a conventional array of light-emittingdiodes 1 includes a substrate 10, a plurality of light-emitting diodeunits 12 arranged in two-dimension on the substrate 10, wherein each ofthe light-emitting diode units 12 includes a light-emitting stackcomprising a p-type semiconductor layer 121, a light-emitting layer 122,and an n-type semiconductor layer 123. These light-emitting diode units12 are formed by patterning a light-emitting stack with an etchingprocess to form trenches 14 by which the light-emitting diode units 12are defined. Since the substrate 10 is not conductive, trenches 14formed between the plurality of the light-emitting diode units 12 makethe light-emitting diode unit 12 electrically insulated from each other.Further, the light-emitting diode units 12 are partially etched toexpose the n-type semiconductor layer 123, and a first electrode 18 anda second electrode 16 are respectively formed on the exposed region ofthe n-type semiconductor layer 123 and a p-type semiconductor layer 121.Then based on a circuit design, conductive wiring structures 19 are usedto form connection between the plurality of light-emitting diode units12, the first electrode 18, and the second electrode 16, and theplurality of light-emitting diode units 12 is electrically connected inseries or in parallel. For example, if a serial circuit is formed, aDirect Current (DC) High Voltage LED (HV LED) is formed.

Nevertheless, a device formed by this process often has a decreasedoverall luminous intensity because of the light absorption between thelight-emitting diode units 12. In addition, for a device formed by thisprocess, the light-emitting diode units 12 are formed by patterning alight-emitting stack with an etching process to form the trenches 14 bywhich the light-emitting diode units 12 are defined. Therefore,different devices includes different light-emitting diode units 12 fromdifferent parts of the substrate, and there is a poor uniformity betweendevices on optical characteristics or electrical characteristics.

SUMMARY OF THE DISCLOSURE

The present disclosure provides a light-emitting device comprises asubstrate with a topmost surface; a first semiconductor stack arrangedon the substrate, and comprising a first light-emitting layer separatedfrom the topmost surface by a first distance; a second semiconductorstack arranged on the substrate, and comprising a second light-emittinglayer separated from the topmost surface by a second distance; and athird semiconductor stack arranged on the substrate, and comprisingthird light-emitting layer separated from the topmost surface by a thirddistance; wherein the first semiconductor stack, the secondsemiconductor stack, and the third semiconductor stack are configured toemit different color lights; and wherein the second distance isdifferent form the first distance and the third distance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a top view of a substrate used in a manufacturing method ofa light-emitting device in accordance with an embodiment of the presentdisclosure.

FIGS. 2A to 2E show a separating method for the manufacturing method ofthe light-emitting device in accordance with one embodiment of thepresent disclosure.

FIGS. 3A to 3E show a manufacturing method of a light-emitting device inaccordance with the first embodiment of the present disclosure.

FIG. 3F shows a manufacturing method of a light-emitting device inaccordance with the fourth embodiment of the present disclosure.

FIG. 4 shows a manufacturing method of a light-emitting device inaccordance with the fifth embodiment of the present disclosure.

FIGS. 5A to 5C show a manufacturing method of a light-emitting device inaccordance with the sixth embodiment of the present disclosure.

FIG. 6 shows a distribution from an actual measurement result of asubstrate used in a manufacturing method of a light-emitting device inaccordance with an embodiment of the present disclosure. Part (a)illustrates determination of a first region and a second region based ona measurement result of the luminous intensity values; Part (b)illustrates determination of a first region and a second region based ona measurement result of a dominant wavelength.

FIGS. 7A and 7B show a conventional array of light-emitting diodes.

DETAILED DESCRIPTION OF THE DISCLOSURE

FIG. 1 shows a top view of a substrate used in a manufacturing method ofa light-emitting device in accordance with an embodiment of the presentdisclosure. There are a plurality of blocks of semiconductor stack onthe substrate 101, such as blocks of semiconductor stack 131, 132, 133,134 and 135. These blocks of semiconductor stack are formed bypatterning a semiconductor stack (not shown), wherein patterning means aprocess performed on the semiconductor stack covered with a photo-resistand then subject to exposure, development, and then etching to formpatterns. After patterning, a plurality of trenches 104 v, 104 h areformed, and the semiconductor stack is divided by the trenches 104 v,104 h into the aforementioned plurality of blocks of semiconductorstack. However, the method for patterning is not limited to thisprocess. There are other methods, for example, a direct cutting bylaser. Further, the aforementioned semiconductor stack can be grown onthe substrate 101. That is, the substrate 101 is a growth substrate forthe semiconductor stack. In another embodiment, the semiconductorstacked is formed on another growth substrate, and then thesemiconductor stack is transferred to the substrate 101 with a transfertechnique. In this case, there may be further an adhesive layer (notshown) between the semiconductor stack (or the block of semiconductorstack) and the substrate 101. The transfer technique is well known to aperson having ordinary skill in the art, and therefore is notillustrated here.

It is noted that, in the present embodiment, the plurality of blocks ofsemiconductor stack may have different optical characteristics orelectrical characteristics, and an optical characteristic value or anelectrical characteristic value for each block of semiconductor stackcan be measured by a measurement step. Based on a predetermineddifferential value for the optical characteristic value or theelectrical characteristic value, the blocks of semiconductor stack areclassified into being located in a first region or a second region onthe substrate 101. The optical characteristic values, for example, are aluminous intensity or a wavelength, and the wavelength can be a dominantwavelength or a peak wavelength. The electrical characteristic value,for example, is a forward voltage. In the present embodiment, aftermeasuring the luminous intensity of each of blocks of semiconductorstack, according to a predetermined differential value for the luminousintensity, the blocks of semiconductor stack are classified into beingin a first region or a second region on the substrate 101. In thepresent embodiment, the predetermined differential value for theluminous intensity is a difference greater than or equal to 3%. Based onthis, a result of the classification is that the first region issubstantially a circle, as a circular area surrounded by a circularborderline 103 shown in the figure, and the second region is an annularshape surrounding the first region, as the annular shape outside thecircular borderline 103 shown in the figure. The blocks of semiconductorstack in the first region have close values in the luminous intensity,and the blocks of semiconductor stack in the second region have closevalues in the luminous intensity. In the present embodiment, the blocksof semiconductor stack in the first region, such as the blocks ofsemiconductor stack 131, 132, and 133, have an average luminousintensity of 4400 mcd, and a standard deviation for the luminousintensity values of the blocks of semiconductor stack in this region isabout 0.5˜1.5 mcd. Meanwhile, the blocks of semiconductor stack in thesecond region, such as the blocks of semiconductor stack 134 and 135,have an average luminous intensity of 4000 mcd, and a standard deviationfor the luminous intensity values of the blocks of semiconductor stackin this region is about 0.5˜1.5 mcd. The differential value for theluminous intensity values between the blocks of semiconductor stack inthe first region and the second region is about 10%((4400−4000)/4000=10%), which is greater than or equal to 3%.

In addition to the luminous intensity, in other embodiments, thedifference in optical characteristics to distinguish the first regionand second region may be a difference in a peak wavelength or a dominantwavelength which is greater than or equal to 1 nm. And the difference inelectrical characteristics may be a difference in a forward voltagewhich is greater than or equal to 2%. FIG. 6 shows a distribution froman actual measurement result. Part (a) illustrates a classificationbased on a measurement result of the luminous intensity values, whereina first region and a second region are determined based on thepredetermined differential value for the luminous intensity. In thepresent embodiment, the predetermined differential value for theluminous intensity is a differential value greater than or equal to 3%.As shown in part (a), the luminous intensity measured for each of theblocks of semiconductor stack is indicated by a color (gray scale in thefigure). For different colors (gray scales in the figure), a luminousintensity value can be found by referring to an indication below whichshows a relationship between the luminous intensity value and the color.As enclosed by the dashed circle in the figure, the first regionincludes mainly red and orange colors (both gray scales in the figure),wherein the red color represents a luminous intensity of 130 mcd, andthe orange color represents a luminous intensity of 129 mcd. Only a fewof blocks of semiconductor stack inside the dashed circle are in greencolor (gray scale in the figure) which represents a luminous intensityof 124 mcd. The first region is substantially in a circular shape, withan average luminous intensity of about 129 mcd. The second region issubstantially an annular shape surrounding the first region describedabove, and includes mainly blocks of semiconductor stack in a greencolor (gray scale in the figure) which represents a luminous intensityof 124 mcd. Only a few of blocks of semiconductor stack inside thesecond region are in red color (gray scale in the figure) whichrepresents a luminous intensity of 130 mcd, and in orange color (grayscale in the figure) which represents a luminous intensity of 129 mcd.An average luminous intensity of the second region is about 124 mcd.That is, the average luminous intensity of the first region is greaterthan the average luminous intensity of the second region, by adifferential value of about 4% ((129−124)/124=4%), which is greater thanor equal to 3%. Part (b) illustrates a classification based on ameasurement result of a dominant wavelength (WLD), wherein a firstregion and a second region are determined based on the predetermineddifferential value for the dominant wavelength. In the presentembodiment, the predetermined differential value for the dominantwavelength is a differential value greater than or equal to 1 nm. Asshown in part (b), the first region (as enclosed by the dashed circle inthe figure) is substantially in a circular shape, with an averagedominant wavelength of about 685 nm. The second region is substantiallyan annular shape surrounding the first region above, with an averagedominant wavelength of about 683 nm. An average dominant wavelength ofthe first region is greater than the average dominant wavelength of thesecond region, by a differential value of about 2 nm, which is greaterthan a predetermined differential value for the dominant wavelength of 1nm.

FIGS. 2A-2E show a separating method for the manufacturing method of thelight-emitting device in accordance with one embodiment of the presentdisclosure. As mentioned in the FIG. 1, a semiconductor stack 202 is ona substrate 201 as shown in FIG. 2A, wherein the semiconductor stack 202includes a first conductive type semiconductor layer 202 a, alight-emitting layer 202 b on the first conductive type semiconductorlayer 202 a, and a second conductive type semiconductor layer 202 c onthe light-emitting layer 202 b. The first conductive type semiconductorlayer 202 a and the second conductive type semiconductor layer 202 c areof different conductive type. For example, the first conductive typesemiconductor layer 202 a is n-type semiconductor layer, and the secondconductive type semiconductor layer 202 c is p-type semiconductor layer.The first conductive type semiconductor layer 202 a, the light-emittinglayer 202 b, and the second conductive type semiconductor layer 202 cinclude III-V group material, such as AlGaInP series materials orAlGaInN series materials. As shown in FIG. 2B, after performing theaforementioned patterning step, a plurality of the trenches 212 having awidth d is formed, and the semiconductor stack 202 is patterned into aplurality of blocks of semiconductor stack 231, 232, 233, 234 and 235,which are respectively corresponding to blocks of semiconductor stack131, 132, 133, 134 and 135 in FIG. 1, and have the luminous intensityvalues as illustrated in FIG. 1, and therefore are classified to thefirst region or the second region accordingly. That is, blocks ofsemiconductor stack 231, 232, and 233 are in the first regionillustrated in FIG. 1, and have the luminous intensity values of 4400mcd. The blocks of semiconductor stack 234 and 235 are in the secondregion illustrated in FIG. 1, and have the luminous intensity values of4000 mcd. There is a difference greater than 3% in luminous intensitybetween the blocks of semiconductor stack 231, 232, and 233, and theblocks of semiconductor stack 234 and 235. And then, to facilitate aseparating step, a first sacrificial layer 211 is formed on the blocksof semiconductor stack which are to be removed. In this embodiment, theblocks of semiconductor stack 232 and 234 are to be removed. The firstsacrificial layer 211 may be formed by forming a layer for the firstsacrificial layer 211 on the whole surface of the substrate 201, andthen selectively leaving the first sacrificial layer 211 on the blocksof semiconductor stack 232 and 234 which are to be removed bylithography and etching process. It is noted that, the person havingordinary skill in the art realizes the order for the above-mentionedprocesses may be altered. That is, the process to form the firstsacrificial layer 211 on the blocks of semiconductor stack 232 and 234which are to be removed is performed first, and then the aforementionedpatterning process is carried out by a lithography and etching processto pattern the semiconductor stack 202 into the plurality of blocks ofsemiconductor stack 231, 232, 233, 234 and 235. FIG. 2C shows theseparating step which includes providing a first temporary substrate 221is performed, and the first temporary substrate 221 and the firstsacrificial layer 211 are bonded together. And then, as shown in FIG.2D, the blocks of semiconductor stack 232 and 234 which are to beremoved are separated from the substrate 201. During this process, alaser may be irradiated at an interface between the blocks ofsemiconductor stack 232 and 234 which are to be removed and thesubstrate 201 for facilitating the separation. Further, thesemiconductor stack 202 may be formed in advance on other growthsubstrate and then transferred to the substrate 201 by a transferringtechnique. In this case, when transferring the semiconductor stack 202to the substrate 201, a sacrificial layer (not shown) may be selectivelyformed in advance on positions of the blocks of semiconductor stack 232and 234 which are to be removed. The sacrificial layer is a fragilematerial or has a weak adhesion to the substrate 201, so that the blocksof semiconductor stack 232 and 234 which are to be removed can beseparated from the substrate 201 more easily during the separatingprocess.

FIG. 2E shows the status after the separating process. The blocks ofsemiconductor stack 232 and 234 are separated from the substrate 201,while the blocks of semiconductor stack 231, 233, and 235 are keptremained on the substrate 201. It is noted that, both of the firsttemporary substrate 221 and the blocks of semiconductor stack 232 and234 thereon, and the substrate 201 and the blocks of semiconductor stack231, 233, and 235 thereon can be used in the manufacturing methods forthe light-emitting device in the following embodiments.

FIGS. 3A to 3E show a manufacturing method for a light-emitting devicein accordance with a first embodiment of the present disclosure. Asshown in FIG. 3A, a permanent substrate 301 is provided first, whereinthis permanent substrate 301 has a first surface 301P1 and a secondsurface 301P2. In the present embodiment, the permanent substrate 301further has a third surface 301P3. As shown in the figure, the firstsurface 301P1 and the second surface 301P2 are non-coplanar. In oneembodiment, this non-coplanar situation is caused by lithography andetching processes applied to a permanent substrate which originally hasa flat surface. The material for the permanent substrate 301 may beglass, sapphire (Al₂O₃), or silicon (Si) substrate.

Subsequently, as shown in FIG. 3B, the block of semiconductor stack 234in FIG. 2E is bonded to the first surface 301P1 of the permanentsubstrate 301. For example, when the material of the permanent substrate301 is a sapphire substrate, the block of semiconductor stack 234 can bedirectly bonded to the permanent substrate 301 under appropriatetemperature and pressure, such as a temperature of about 300° C.˜420°C., and a pressure of about 11000 Kgf˜14000 Kgf. The bonding can also becarried out optionally with a bonding layer 312B1. For example, when thematerial of the permanent substrate 301 is sapphire, silicon dioxide canbe used as the bonding layer 312B1. The block of semiconductor stack 234is then separated from the first temporary substrate 221. During thisprocess, a laser (not shown) is used to irradiate at an interfacebetween the block of semiconductor stack 234 and the first sacrificiallayer 211 for facilitating the separation.

Then, as shown in FIG. 3 C, the block of semiconductor stack 232 isbonded to the second surface 301P2 of the permanent substrate 301. Thisbonding is substantially similar to the bonding of the block ofsemiconductor stack 234 illustrated above, and therefore is notillustrated again.

As described in FIG. 2A, in one embodiment, blocks of semiconductorstack 231, 232, 233, 234, and 235 are respectively corresponding toblocks of semiconductor stack 131, 132, 133, 134 and 135 in FIG. 1, andhave the luminous intensity values as illustrated in FIG. 1. That is,blocks of semiconductor stack 231, 232, and 233 are in the first regionillustrated in FIG. 1, and have the luminous intensity values of 4400mcd. The blocks of semiconductor stack 234 and 235 are in the secondregion illustrated in FIG. 1, and have the luminous intensity values of4000 mcd. There is a difference greater than 3% in luminous intensitybetween the blocks of semiconductor stack 231, 232, and 233, and theblocks of semiconductor stack 234 and 235. By using the manufacturingmethod in the above embodiment, a light-emitting device can be formedwith a rearrangement or a reallocation of blocks of semiconductor stacklocated originally in two regions which have great difference in opticalcharacteristics or electrical characteristics. For example, when aconventional manufacturing method in the background is used, blocks ofsemiconductor stack 132 and 133 may be combined to form a device (deviceA) because of their close locations and being substantially in the sameregion (Please refer to FIG. 1 and FIG. 2B). Similarly, blocks ofsemiconductor stack 134 and 135 may be combined to form another device(device B) because of their close locations and being substantially inthe same region (Please refer to FIG. 1 and FIG. 2B). Therefore, deviceA includes two blocks of semiconductor stack which have an averageluminous intensity of 4400 mcd, while device B includes two blocks ofsemiconductor stack which have an average luminous intensity of 4000mcd. The uniformity of luminous intensity for these two devices is poor.In contrast, for a light-emitting device formed by using themanufacturing method in the above embodiment, such as the one shown inFIG. 3C, there is a block of semiconductor stack 234 on the firstsurface 301P1, while there is a block of semiconductor stack 232 on thesecond surface 301P2, wherein the block of semiconductor stack 234 isoriginally located in the second region in FIG. 1 which has an averageluminous intensity of 4000 mcd, while the block of semiconductor stack232 is originally located in the first region in FIG. 1 which has anaverage luminous intensity of 4400 mcd. That is, blocks of semiconductorstack originally located in two regions which have great difference inoptical characteristics or electrical characteristics are rearranged orreallocated to form a combination. Similarly, by using the manufacturingmethod in the above embodiment, another device which includes the blockof semiconductor stack 235 and the block of semiconductor stack 233 canbe formed, wherein the block of semiconductor stack 235 is originallylocated in the second region in FIG. 1 which has an average luminousintensity of 4000 mcd, while the block of semiconductor stack 233 isoriginally located in the first region in FIG. 1 which has an averageluminous intensity of 4400 mcd. There is a better performance for theuniformity of luminous intensity for these two devices above.

In addition, by bonding to the permanently substrate 301, the blocks ofsemiconductor stack 234 and 232 are located respectively on twonon-coplanar surfaces, that is, the first surface 301P1 and the secondsurface 301P2. This reduces the mutual absorption of light between theblocks of semiconductor stack, and leads to a better performance on anoverall luminous intensity.

By using the aforementioned bonding method, another block ofsemiconductor stack 23X can be bonded to the third surface 301P3, asshown in FIG. 3D. There is no particular limitation for the block ofsemiconductor stack 23X. For the person having ordinary skill in theart, what is important is to rearrange or reallocate blocks ofsemiconductor stack to form a combination to produce a device which hasa better performance on the uniformity in optical characteristics orelectrical characteristics. Subsequently, as shown in FIG. 3E, theblocks of semiconductor stack are partially etched to expose their firstconductive type semiconductor layer 202 a by using lithography andetching processes, and a dielectric layer 320 is formed on sidewalls ofthe blocks of semiconductor stack. A metal line 330 is formed betweenthe blocks of semiconductor stack to electrically connect the blocks ofsemiconductor stack in a serial or parallel connection. As shown in FIG.3E, the metal line 330 electrically connects the blocks of semiconductorstack in a serial connection.

Although in this embodiment all the two blocks of semiconductor stackbonded to the permanent substrate 301 are selected from the blocks ofsemiconductor stack separated from the substrate 201 as shown in FIG.2E, the person having ordinary skill in the art understands this is nota limitation. For example, the blocks of semiconductor stack 231, 233,and 235 are kept remained on the substrate 201, and in a secondembodiment it can be these blocks of semiconductor stack which are keptremained on the substrate 201 that are bonded to the permanent substrate301. This embodiment is substantially the same as those illustrated inFIGS. 3B to 3E, and can be realized simply by correspondentlysubstituting the first temporary substrate 221 and the blocks ofsemiconductor stack thereon in these figures with the substrate 201 andthe blocks of semiconductor stack 231, 233, and 235 thereon. Therefore,the figures for this embodiment are not presented in the specification.In this embodiment, the bonding process is an alignment bonding of thesubstrate 201 to the permanent substrate 301, so that the blocks ofsemiconductor stack 231, 233, and 235 are respectively bonded tosurfaces which they are intended to be bonded. And then the substrate201 is moved away from the permanent substrate 301, so that the blocksof semiconductor stack which are bonded are separated from the substrate201. In the third embodiment, the blocks of semiconductor stack 231,233, and 235 which are kept remained on the substrate 201 can be firstseparated from the substrate 201 as illustrated in the first embodiment,and then bonded to the permanent substrate 301. In this case, thebonding process is to bond the blocks of semiconductor stack 231, 233,and 235 to a second temporary substrate. After the bonding process, theblocks of semiconductor stack 231, 233, and 235 are separated from thesubstrate 201. And then an alignment bonding of the second temporarysubstrate to the permanent substrate 301 is performed so that the blocksof semiconductor stack 231, 233, and 235 are respectively bonded tosurfaces which they are intended to be bonded. And then the secondtemporary substrate is moved away from the permanent substrate 301 sothat the blocks of semiconductor stack which are bonded are separatedfrom the second temporary substrate.

Although the first embodiment illustrates the block of semiconductorstack (i.e., the block of semiconductor stack 234) on the first surface301P1 of the permanent substrate 301, and the block of semiconductorstack (i.e., the block of semiconductor stack 232) on the second surface301P2 of the permanent substrate 301 are both from the samesemiconductor stack 202, this is not a limitation. That is, in otherembodiment, the block of semiconductor stack on the first surface 301P1and the block of semiconductor stack on the second surface 301P2 can befrom different semiconductor stacks. Further, even in the case that theblocks of semiconductor stack are from the same semiconductor stack,they can be bonded to the permanent substrate 301 through the firsttemporary substrate 221, the substrate 201, or the second temporarysubstrate as illustrated respectively in the foregoing embodiments.

FIG. 3F shows the fourth embodiment of the present disclosure. Thisembodiment is substantially the same as the first embodiment, but thepermanent substrate 301 in the first embodiment is substituted byanother permanent substrate 301′. In contrast to the permanent substrate301 comprising the first surface 301P1, the second surface 301P2, andthe third surface 301P3 which are non-coplanar, the permanent substrate301′ in this embodiment includes a first surface 301′P1, a secondsurface 301′P2, and a third surface 301′P3 which are coplanar. But whenthe blocks of semiconductor stack are bonded to the permanent substrate301′, they are non-coplanar because bonding layers of differentthicknesses are used. For example, the block of semiconductor stack 234is bonded to the first surface 301′P1 with a first bonding layer 312′B1,while the block of semiconductor stack 232 is bonded to the secondsurface 301′P2 with a second bonding layer 312′B2. The first bondinglayer 312′B1 and the second bonding layer 312′B2 have differentthicknesses so that the block of semiconductor stack 234 and the blockof semiconductor stack 232 are non-coplanar.

Although it is illustrated in the first embodiment that a plurality ofregions on the substrate as shown in FIG. 1 may be determined based ondifference in optical characteristics or electrical characteristics, anda plurality of blocks of semiconductor stack from these differentregions are used to be bonded, this is not a limitation to the presentapplication. FIG. 4 shows a fifth embodiment of the present disclosure.In this embodiment, the blocks of semiconductor stack are not able to beclassified into different regions on the substrate as shown in FIG. 1based on difference in optical characteristics or electricalcharacteristics. However, based on a measurement result of opticalcharacteristics or electrical characteristics, these blocks ofsemiconductor stack on the same substrate are still able to berespectively classified into a typical bin group, a low bin group, and ahigh bin group, wherein the optical characteristic value or theelectrical characteristic value in the high bin group is greater thanthat in the typical bin group, and the optical characteristic value orthe electrical characteristic value in the typical bin group is greaterthan that in the low bin group. For example, FIG. 4 shows themeasurement result of luminous intensity for these blocks ofsemiconductor stack on the same substrate. After the measurement, datafor the location on the substrate and luminous intensity value for eachblock of semiconductor stack can be stored in a machine. The horizontalaxis in the figure is the luminous intensity, and the vertical axis isan amount of blocks of semiconductor stack for the correspondentluminous intensity. As shown in the figure, group (a) is the low bingroup which has an average luminous intensity of 700 mcd. Group (b) isthe typical bin group which has an average luminous intensity of 900mcd, and group (c) is the high bin group which has an average luminousintensity of 1200 mcd. By using the separating method illustrated inFIG. 2 and the bonding method illustrated in FIG. 3, and based on datafor the location on the substrate and luminous intensity value for eachblock of semiconductor stack which are stored in the machine, properblocks of semiconductor stack can be selected to be bonded on thepermanent substrate 301 as shown in FIG. 3A, and rearrangement of blocksof semiconductor stack is achieved. As shown on the right part of FIG.4, if a device is designed to have five blocks of semiconductor stack,then with the rearrangement, five blocks of semiconductor stack in thetypical bin group (with an average luminous intensity of 900 mcd) areselected to be bonded on the permanent substrate 301 shown in FIG. 3A toform a device C. For another device D, three blocks of semiconductorstack in the low bin group (with an average luminous intensity of 700mcd) are selected to be bonded on the permanent substrate 301 shown inFIG. 3A, and two blocks of semiconductor stack in the high bin group(with an average luminous intensity of 1200 mcd) are selected to bebonded on the same permanent substrate 301 to form the device D. Theblocks of semiconductor stack on different location of the substrate mayhave great difference in optical characteristics or electricalcharacteristics. For example, there is relatively higher luminousintensity of 1200 mcd as those in the high bin group while there isrelatively lower luminous intensity of 700 mcd as those in the low bingroup. However, after the blocks of semiconductor stack are rearrangedin the present embodiment, the uniformity between the devices isimproved and controlled. For example, both the device C and the device Dhave luminous intensity of substantially 4500 mcd. In addition, asmentioned in the first embodiment, after being bonded to the permanentsubstrate 301, the blocks of semiconductor stack are locatedrespectively on different non-coplanar surfaces. This reduces the mutualabsorption of light between the blocks of semiconductor stack, and leadsto a better performance on an overall luminous intensity.

It is noted that, in the above embodiments, the optical characteristicvalues or characteristic electrical values can be obtained by actuallycarrying out measuring all blocks of semiconductor stack or by samplingsome of them before the separating process. In a case where themanufacturing process is stable, a predetermined statistic value for theoptical characteristic values or characteristic electrical values can beobtained through statistics from a certain number of measuring. Forexample, a boundary of the first region and the second region in theFIG. 1 can be checked through statistics from a certain number ofmeasuring in a case where the manufacturing process is stable. That is,a predetermined value for a radius of the first region, and thecorrespondent optical characteristic values or correspondentcharacteristic electrical values in this case are obtained, and actualone by one measuring for all output substrates are not necessary.

As mentioned in FIG. 3E for the first embodiment, the blocks ofsemiconductor stack bonded to the permanent substrate 301 can be fromdifferent semiconductor stacks. For example, the block of semiconductorstack on the first surface 301P1 and the block of semiconductor stack onthe second surface 301P2 can be from different semiconductor stacks fromdifferent substrates. This kind of application can further be used toimprove the color rendering of a light-emitting device, that is, toraise the CRI value of a light-emitting device. This kind of applicationis shown as FIGS. 5A to 5C, which is the sixth embodiment of the presentdisclosure. As shown in FIG. 5A, blocks of semiconductor stack 501 a and501 b are respectively bonded to the permanent substrate 501, whereinthe bonding method is substantially as illustrated in the firstembodiment shown in FIG. 3. However, the two blocks of semiconductorstack 501 a and 501 b are separated from different semiconductor stacksfrom different substrates. For example, the block of semiconductor stack501 a is separated from a semiconductor stack which can emit light witha dominant wavelength of about 620 nm to 645 nm, while the block ofsemiconductor stack 501 b is separated from a semiconductor stack whichcan emit light with a dominant wavelength of about 595 nm to 620 nm.That is, the two blocks of semiconductor stack 501 a and 501 b areseparated from different substrates, and the block of semiconductorstack 501 a can emit light with a red color, while the block ofsemiconductor stack 501 b can emit light with an orange color. Thus,when the two blocks of semiconductor stack are bonded to the permanentsubstrate 501, a light-emitting device 500 a is formed, which can beused to replace a chip which includes only a single semiconductor stackfor the red or orange light in a conventional warm white light-emittingdevice. That is, the light-emitting device 500 a can be used incombination with a blue light source and YAG. Because the warm whitelight from this combination includes light with different dominantwavelengths from the two blocks of semiconductor stack 501 a and 501 b,it has a better color rendering in comparison with warm white lightformed by the above chip which includes only a single semiconductorstack.

As shown in FIG. 5B, in addition to the two blocks of semiconductorstack 501 a and 501 b bonded to the permanent substrate 501, a block ofsemiconductor stack 501 c to provide blue light is also directly bondedto the permanent substrate 501. A light-emitting device 500 b is formeddirectly as a warm white light source, wherein the three blocks ofsemiconductor stack 501 a, 501 b, and 501 c are separated from differentsemiconductor stacks from different substrates. For example, the blockof semiconductor stack 501 a is separated from a semiconductor stackwhich can emit light with a dominant wavelength of about 620 nm to 645nm. The block of semiconductor stack 501 b is separated from asemiconductor stack which can emit light with a dominant wavelength ofabout 595 nm to 620 nm. The block of semiconductor stack 501 c isseparated from a semiconductor stack which can emit light with adominant wavelength of about 440 nm to 460 nm. That is, the three blocksof semiconductor stack 501 a, 501 b, and 501 c are separated fromdifferent substrates, and the block of semiconductor stack 501 a canemit light with a red color, the block of semiconductor stack 501 b canemit light with an orange color, and the block of semiconductor stack501 c can emit light with a blue color.

Further, as shown in FIG. 5C, in addition to the three blocks ofsemiconductor stack 501 a, 501 b, and 501 c bonded to the permanentsubstrate 501, a fourth block of semiconductor stack 501 d is furtherbonded to the permanent substrate 501. The four blocks of semiconductorstack 501 a, 501 b, 501 c, and 501 d are separated from differentsemiconductor stacks from different substrates. The dominant wavelengthsand colors of light emitted by blocks of semiconductor stack 501 a, 501b, and 501 c are the same as those illustrated in FIG. 5B above, and theblock of semiconductor stack 501 d can emit light with a dominantwavelength of about 510 nm to 530 nm, i.e., a green color. Because theblock of semiconductor stack 501 d emits light with a dominantwavelength in a green color, the warm white light from thislight-emitting device 500 c has a higher CRI value than that of thelight-emitting device 500 b in FIG. 5B. That is, the color rendering ofthe light-emitting device 500 c is even better.

The above-mentioned embodiments are only examples to illustrate thetheory of the present invention and its effect, rather than be used tolimit the present application. Other alternatives and modifications maybe made by a person having ordinary skill in the art of the presentapplication without departing from the spirit and scope of theapplication, and are within the scope of the present application.

What is claimed is:
 1. A light-emitting device, comprising: a substrate with a topmost surface; a first semiconductor stack arranged on the substrate, and comprising a first light-emitting layer separated from the topmost surface by a first distance; a second semiconductor stack arranged on the substrate, and comprising a second light-emitting layer separated from the topmost surface by a second distance; and a third semiconductor stack arranged on the substrate, and comprising third light-emitting layer separated from the topmost surface by a third distance; wherein the first semiconductor stack, the second semiconductor stack, and the third semiconductor stack are configured to emit different color lights; wherein the second distance is different form the first distance and the third distance.
 2. The light-emitting device of claim 1, wherein the first semiconductor stack, the second semiconductor stack and the third semiconductor stack are configured to emit red light, green light and blue light, respectively.
 3. The light-emitting device of claim 1, wherein the first semiconductor stack and the third semiconductor stack are made of a same material system.
 4. The light-emitting device of claim 1, further comprising a dielectric layer formed on the first semiconductor stack, the second semiconductor stack and the third semiconductor stack.
 5. The light-emitting device of claim 1, wherein the first semiconductor stack, the second semiconductor stack and the third semiconductor stack are electrically connected with one another.
 6. The light-emitting device of claim 1, wherein the first semiconductor stack, the second semiconductor stack and the third semiconductor stack are electrically connected in parallel with one another.
 7. The light-emitting device of claim 1, further comprising a first bonding layer arranged between the substrate and the first semiconductor stack.
 8. The light-emitting device of claim 7, further comprising a second bonding layer arranged between the substrate and the second semiconductor stack.
 9. The light-emitting device of claim 8, wherein the first bonding layer and the second bonding layer have different thicknesses.
 10. The light-emitting device of claim 8, further comprising a third bonding layer arranged between the substrate and the third semiconductor stack, wherein the third bonding layer and the second bonding layer have different thicknesses.
 11. The light-emitting device of claim 1, wherein the first semiconductor stack and the second semiconductor stack are not coplanar with each other with their uppermost surfaces.
 12. The light-emitting device of claim 11, wherein the first semiconductor and the third semiconductor stack are coplanar with each other with their uppermost surfaces. 